A father age 45+ when a child is born. A fossil dad is usually unable to play with his kids due to physical limitations brought upon by advanced age. Fossil dads combine the grumpiness, intolerance, and ignorance of today's price levels of a grandparent with the lack of understanding of a regular-age dad. Infrequently spotted with fossil moms.

There are two types of fossil dads:

1) The most common by far are dads who had children with Mom 1 on a normal schedule, then shacked up with younger Mom 2 who wanted her own kids and found himself awake at 3am cleaning poop off his sleeve for the first time in 20 years.

2) Less common are the first-timers who, for reasons of religious commitment or other strictures took a little extra time to find "the right woman for him."

Kevin Costner is a famous fossil dad with the resources to buy his way out of definition #1 above.